#include <bits/stdc++.h>
#define all(v) v.begin(),v.end()
#define F first
#define S second
#define mid ((l+r)>>1)
using namespace std;
typedef long long ll;
typedef pair<ll,ll>pll;
const ll oo= 1e5+9;
const ll inf=1e18;
struct node
{
ll t,l,r,c;
} a[oo];
struct seg
{
seg *l=0,*r=0;
ll mn=inf;
}*root;
bool cmp(const node&A,const node&B)
{
return A.r < B.r;
}
ll n,m;
void up(seg*&d,ll l,ll r,ll id,ll val)
{
if(l==r)
return void(d-> mn = min(d->mn ,val));
if(id<=mid)
{
if(d->l==0)
d->l = new seg;
up(d->l,l,mid,id,val);
}
else
{
if(d->r==0)
d->r = new seg;
up(d->r,mid+1,r,id,val);
}
d-> mn = inf;
if(d->l!=0)
d->mn = d->l->mn;
if(d->r!=0)
d->mn = min(d->mn,d->r->mn);
}
ll best(seg*&d,ll l,ll r,ll lx)
{
if(d==0||r<lx)
return inf;
if(lx<=l)
return d->mn;
return min(best(d->l,l,mid,lx),best(d->r,mid+1,r,lx));
}
void solve()
{root = new seg();
cin>>n>>m;
for(ll i=0; i<m; i++)
{
cin>>a[i].t>>a[i].l>>a[i].r>>a[i].c;
}
sort(a,a+m,cmp);
ll ans=inf;
up(root,0,n,0,0);
for(ll i=0; i<m; i++)
{
ll x= a[i].c + best(root,0,n,a[i].l-1);
if(a[i].r==n)
ans=min(ans,x);
up(root,0,n,a[i].r,x);
}
if(ans>=inf)
cout<<-1;
else
cout<<ans;
}
int main()
{
ios::sync_with_stdio(0),cin.tie(0);
ll tt=1;
// cin>>tt;
while(tt--)
solve();
return 0;
}
